Roller conveyors of this type have been known, a typical example of which is described in Japanese Patent Application Laid-Open Publication No. 57-160807. This known roller conveyor includes a main frame consisting of parallel rails, and a multiplicity of rollers carried by the main frame for free rotation only to form a conveyance track, with a casing mounted to the main frame through a support bracket or the like. The casing is provided with pins extending in the axial direction of the rollers, and on each of the pins are rotatably supported a wheel abuttable against a pair of adjacent rollers and a sprocket rotatable integrally with and positioned at outer side of the wheel. A drive chain supported and guided within the casing is in engagement with the sprockets. Between the casing and each pin is provided a diaphragm type drive means for vertically moving the pin.
According to the arrangement of the known roller conveyor, each wheel is rotated by the drive chain via the associated sprocket, and the rotation of the wheel is transmitted to the pair of rollers which are in abutment with the wheel. Thus, the multiplicity of rollers are rotated to enable articles to be conveyed on the conveyance track. Individual pins are moved upward and downward by controlling working fluid supply to and discharge from the associated diaphragms, so that the mode of operation is switched over from a driving mode in which each wheel is in abutment with adjacent rollers to a non-driving mode in which each wheel is separated from adjacent rollers and vice versa whereby a conveying force for individual articles is supplied or shut off. In this way, conveying operation is controlled to prevent individual articles from colliding with one another.
However, such arrangement involves a problem that when articles having a large width are to be conveyed, longer and heavier rollers are required, which in turn necessitates a main frame of greater rigidity and larger size. Another problem is that the increase in the weight of rollers requires a greater driving force to be given through each wheel. A further problem is that forceful inertial rotation occurs when driving is stopped, which fact requires the provision of a large number of stoppers for accurately stopping the run of articles.